A U-Boat with Japanese weapons... You should create devices for German weapons. I have the monsoon boats and transport subs (German and Italien) in my mod,I can send you the data later when at home.
Now, why no mines are being loaded? Port size, base supplies, AS present, mines in the pools?
Btw, there was no type IX/C 41 class - the only sub-variant of the IX/C was the IX/C40.
87 boats of the type IX/C40 have been built, 52 of them were fitted for mine operations and the remaining 35 were not.
They had four bow torpedo tubes and two stern tubes and could carry 22 torpedos - or in minelaying configuration 44 TMA or 66 TMB mines in the torpedo tubes.
So if modelled with a minelaying capacity, it should be a conversion option with either torpedo armament or mines, but not both.
Mines have other submarine ship mines with the port. Space would like to work as a Type KRS. For the same place torpedoes they could carry mines in such numbers ? because in fact mine is at times less than the torpedo, which is three times smaller.
PS. New devices can not be added because there is PBEM.